Fluorinated ketones are useful, reactive chemical intermediates, e.g. to make condensation type polymers, e.g. polyamides, polyimides and polyesters suitable for coatings, electronics and high performance polymers. The ketones can also be reduced to alcohols which also have utility as intermediates. Hexafluoroacetone, for example, is widely used commercially in the manufacture of fluorinated aromatic polyesters, polyamides, and polyimides (see W. K. Appel, B. A. Blech, and M. Stobbe in "Organofluorine Chemistry Principles and Commercial Applications", p 413, Plenum Press, New York, 1993).
Several synthetic methods for perfluorinated ketones have been reported. Few, if any, however, appear to be suitable for all members of the family of perfluoroketones, R.sub.f C(O)R.sub.f, where R.sub.f is a perfluoroalkyl group. For example, the more useful methods for preparing hexafluoroacetone, such as the halogen exchange of hexachloroacetone and the isomerization of hexafluoropropene oxide (for a review of hexafluoroacetone, see C. G. Krespan and W. J. Middleton, Fluorine Chem. Rev, 1 (1967) 145) do not work or do not give pure materials when applied to higher homologs in the series. For this reason other methods have been necessary for these higher molecular weight ketones. Perfluoro-3-pentanone has been prepared by the cesium fluoride catalyzed reaction of perfluoropropionyl fluoride with tetrafluoroethylene (A. Nakahara, Y. Izeki, and J. Nakajima, Jpn. Kokai Tokyo Koho JP 01, 226, 846; CA 112:P118260u). Perfluoro-4-heptanone has been prepared by the reaction of sodium ethoxide with ethyl perfluorobutyrate (D. W. Wiley, U.S. Pat. No. 3,091,463 Mar. 28, 1963). According to this patent (Wiley's method), one mole of an alkali metal alkoxide is treated with 2 moles of an ester of a fluorinated acid having not less than three carbon atoms in the acid portion of the ester. Although the yield was good, reaction times were long, e.g. several days and involved complex product isolation and dehydration procedures. Perfluoro-4-heptanone has also been prepared in 20% yield by the action of heptafluoromagnesium iodide on ethyl heptafluorobutyrate (A. L. Henne and W. C. Frances, J. Am. Chem. Soc., 75 (1953) 992).
The decarboxylation of salts of haloacetic acids has been used as a means to generate trihalomethide (CF.sub.3.sup.-) ions. For example, salts of trifluoroacetic acid, e.g., CF.sub.3 COOK, were heated in a solvent and the CF.sub.3.sup.- anion generated was reacted with appropriate electrophiles such as SO.sub.2 to generate trifluoromethylated compounds, such as CF.sub.3 SO.sub.2 K (J. R. Desmers, G. Forat, V. Pevere, S. Ratton, N. Rogues, J. Russell, and L. Saint-Jalmes, Abstract O(3) C-5, 15.sup.th International Symposium on Fluorine Chemistry, Vancouver, Canada, August, 1997).
In the case of non-fluorinated anhydrides, the transformation of anhydrides to ketones has found limited use in the preparation of symmetrical ketones (E. H. Man and C. R. Hauser, J. Am. Chem. Soc., 72, (1950), 3294). The catalyst is boron trifluoride (used in large quantity to form a saturated solution), and appears to be limited to anhydrides which have a hydrogen on the carbon adjacent to the carbonyl carbon. In these reactions decarboxylation does not occur until the initially formed products (anhydrides in which one or more hydrogens have been replaced by RC(O) groups) are hydrolyzed. H. Meerwein and D. Vossen, (J. Prakt. Chem., 141 (1934) 149) indicate for the conversion of acetic anhydride to 2,4-pentanedione, for example, the stoichiometry is: 5 CH.sub.3 C(O)OC(O)CH.sub.3 +H.sub.2 O (during work-up).fwdarw.2CH.sub.3 C(O)CH.sub.2 C(O)CH.sub.3 +4CH.sub.3 COOH+2CO.sub.2.